CODEWITHSUNDEEP
java-8
Tiina
Tiina

Reputation: 4797

java stream throws NPE when toMap stores a null value

HashMap allows to store NULL value, but Stream.toMap(r-> r.getName(), r->r.get(obj)) would throw NPE when r.get(obj) returns null? Do I miss something or Stream has a special reason to be more careful than Map? I am trying to use reflection and java8 to achieve (new ObjectMapper()).convertValue(obj, Obj.class);

Upvotes: 3

Views: 4054

Answers (1)

Beri
Beri

Reputation: 11620

Collector.toMap uses HashMap::merge to combine results:

public V merge(K key, V value,
               BiFunction<? super V, ? super V, ? extends V> remappingFunction) {
    if (value == null)
        throw new NullPointerException();
    if (remappingFunction == null)
        throw new NullPointerException();

So it may store null values, but merge does not allow it.

You can do a work around, by using forEach

stream.forEach (
   r-> map.put(r.getName(), r.get(obj))
)

Upvotes: 2

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